Feeling lots of anxiety related symptoms in my body, what's happening?

[ChelseyLu]

Recently, for the last 5 or 6 months, I've been experiencing overwhelming feelings in my body which I'll attempt to list. These come in 'episodes' which can last 20 minutes to hours, usually at night. These feelings are completely overwhelming. I'm unable to do anything but attempt to cope with the feelings that I have. These usually come on by mention, by memory of an 'episode', or at random (when I'm not busy, but this is usually when I'm attempting to sleep). I was professionally diagnosed with depression about 4 years ago, but this is nothing I've experienced before. The symptoms begin as completely physical, but quickly turn into a mental breakdown because the feelings are so horrible.

-Horrible feeling in chest, wouldn't describe it as tightness
-Heart beating fast
-Urge to cry/crying
-Scratching at chest
-Urge to punch/hit things or cause harm in an attempt to end the feeling
-Anger due to the feeling
-Feeling of extreme antsiness. (reminds me of extreme rls?)
-Physical anxiousness
-Inability to sleep or rest
-Thinking of symptoms makes symptoms worse
-Extreme need to stretch, clench and move muscles
-Often I find myself hitting my head to relieve the feeling, atleast for a moment
-Completely removing myself from where I am. This usually means venturing outside at 4am,

I'm sure I'm missing quite a few. It's a horrible feeling in my body, but it starts as a physical issue, which quickly turns into panic. So far, I haven't found any surefire way to calm the feelings. But, they aren't triggered by overthinking, and doesn't begin with anxiety or depression. I have no idea what is happening to me since this all happens very, very suddenly, within seconds.